INACTIVE AEROBIC GRANULES AS BIOSORBENT FOR THE REMOVAL OF ANIONIC AZO DYE ACID RED 14 FROM AQUEOUS SOLUTION: ISOTHERMS, KINETICS AND THERMODYNAMICS

The aim of this study was to determine the feasibility of the use of inactive aerobic granules as a biosorbent for removing Acid Red 14 (AR 14), an anionic azo dye, from aqueous solution. The effects of pH, biosorbent dosage, initial AR 14 concentration, NaCl concentration and temperature on the biosorption were investigated. The results show that initial pH would be the most important parameter affecting AR 14 biosorption and the optimal pH was 2.0. The biosorption capacity increased with an increase in initial dye concentration, but decreased with an increase in biosorbent dosage and NaCl concentration. The Langmuir and Redlich-Peterson isotherms fitted better to the equilibrium data than the Freundlich isotherm. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were applied to fit the experimental data, and the results show that the biosorption of AR 14 followed the pseudo-second-order kinetic model. The thermodynamic analysis indicates that the biosorption process was endothermic in nature and could occur spontaneously. The FTIR analysis revealed that chemical functional groups (e.g., amine, carboxyl, hydroxyl and either) on aerobic granules would be the active binding sites for biosorption of AR 14. These results show that inactive aerobic granules could be employed as a low-cost and alternative biosorbent in the wastewater treatment for the removal of anionic azo dye AR 14.